Lower Ventilatory Capacity Research Articles

The association of vitamin K status with lung function and disease in a general population.

Matrix Gla protein (MGP) is an inhibitor of lung tissue calcification. The plasma level of dephosphorylated-uncarboxylated MGP (dp-ucMGP) is a biomarker of vitamin K status. The present study assessed whether lower vitamin K status (reflected by higher dp-ucMGP) was associated with lung function and lung disease/symptoms. A general population sample of 4092 individuals, aged 24 to 77 years, underwent a health examination including questionnaires, spirometry and measurements of plasma dp-ucMGP. Associations of dp-ucMGP with lung function and self-reported disease/symptoms were estimated using regression models adjusted for age, sex and height. Associations were expressed as β-estimates or odds ratios (ORs) per doubling in dp-ucMGP. Lower vitamin K status (higher dp-ucMGP) was associated with lower forced expiratory volume in 1 s (FEV1) (98 mL; 95% CI: 54-141 mL) and lower forced vital capacity (FVC) (136 mL; 95% CI: 85-187 mL). Dp-ucMGP was not associated with the FEV1/FVC ratio (0.0 percentage points higher than the expected value; 95% CI: -1.0-1.0). Furthermore, lower vitamin K status was associated with COPD (OR 2.24, 95% CI: 1.53-3.27), wheezing (OR 1.81, 95% CI: 1.44-2.28) and asthma (OR 1.44, 95% CI: 1.12-1.83). Lower vitamin K status was associated with lower ventilatory capacity (lower FEV1 and FVC), and with higher risk of self-reported asthma, COPD and wheezing. Vitamin K status was not associated with airflow obstruction (FEV1/FVC ratio).

Investigating the differences in nutritional status between successfully weaned and unsuccessfully weaned respirator patients

Long-term respirator users admitted to intensive care units need to be transferred to a respiratory care center (RCC) for weaning. It may cause malnutrition in critical care patients, which may manifest as a reduction in respiratory muscle mass, lower ventilatory capacity, and decreased respiratory tolerance. This study aimed to assess that if the patients’ nutritional status were improved, it could help RCC patients to wean from respirators. All participants were recruited from the RCC of a medical foundation in the city and Taipei Tzu Chi Hospital. The indicators include serum albumin level, respirator detachment index, maximum inspiratory pressure (PImax), rapid shallow breathing index, and body composition measurements. We recorded the length of hospital stay, mortality, and RCW (respiratory care ward) referral rate for these participants and analyzed the differences in relevant research indicators between those who were and weren’t weaned off. 43 of 62 patients were weaned from respirators, while 19 failed. The resuscitation rate was 54.8%. Patients with respirator weaning had a lower number of RCC admission days (23.1 ± 11.1 days) than respirator-dependent patients (35.6 ± 7.8 days, P < 0.05). The PImax of successfully weaned patients had a greater reduction (− 27.09 ± 9.7 cmH2O) than unsuccessful ones (− 21.4 ± 10.2 cmH2O, P < 0.05). The Acute Physiology and Chronic Health Evaluation II (APACHE II) scores of successfully weaned patients (15.8 ± 5.0) were lower than those who were not (20.4 ± 8.4, P < 0.05). There was no significant difference in serum albumin levels between the two groups. In the successfully weaned patients, the serum albumin concentration was increased from 2.2 ± 0.3 to 2.5 ± 0.4 mg/dL, P < 0.05. Improved nutritional status can help RCC patients to wean from respirators.

Predictors of Expiratory Flow Limitation during Exercise in Healthy Males and Females

It is unclear whether the frequency and mechanisms of expiratory flow limitation (EFL) during exercise differ between males and females. This study aimed to determine which factors predispose individuals to EFL during exercise and whether these factors differ based on sex. We hypothesized that i) EFL frequency would be similar in males and females and ii) in females, EFL would be associated with indices of low ventilatory capacity, whereas in males, EFL would be associated with indices of high ventilatory demand. Data from n = 126 healthy adults (20-45 y, n = 60 males, n = 66 females) with a wide range of cardiorespiratory fitness (81%-182% predicted maximal oxygen uptake) were included in the study. Participants performed spirometry and an incremental cycle exercise test to exhaustion. Standard cardiorespiratory variables were assessed throughout exercise. The tidal flow-volume overlap method was used to assess EFL based on a minimum threshold of 5% overlap between the tidal and the maximum expiratory flow-volume curves. Predictors of EFL during exercise were determined via multiple logistical regression using anthropometric, pulmonary function, and peak exercise data. During exercise, EFL occurred in 49% of participants and was similar between the sexes (females = 45%, males = 53%; P = 0.48). In males, low forced expired flow between 25% and 75% of forced vital capacity and high slope ratio as well as low end-expiratory lung volume, high breathing frequency, and high relative tidal volume at peak exercise were associated with EFL ( P < 0.001; Nagelkerke R2 = 0.73). In females, high slope ratio, high breathing frequency, and tidal volume at peak exercise were associated with EFL ( P < 0.001; Nagelkerke R2 = 0.61). Despite sex differences in respiratory system morphology, the frequency and the predictors of EFL during exercise do not substantially differ between the sexes.

With age a lower individual breathing reserve is associated with a higher maximal heart rate

IntroductionMaximal heart rate (HRmax) is linearly declining with increasing age. Regular exercise training is supposed to partly prevent this decline, whereas sex and habitual physical activity do not. High exercise capacity is associated with a high cardiac output (HR x stroke volume) and high ventilatory requirements. Due to the close cardiorespiratory coupling, we hypothesized that the individual ventilatory response to maximal exercise might be associated with the age-related HRmax. MethodsRetrospective analyses have been conducted on the results of 129 consecutively performed routine cardiopulmonary exercise tests. The study sample comprised healthy subjects of both sexes of a broad range of age (20–86 years). Maximal values of power output, minute ventilation, oxygen uptake and heart rate were assessed by the use of incremental cycle spiroergometry. ResultsLinear multivariate regression analysis revealed that in addition to age the individual breathing reserve at maximal exercise was independently predictive for HRmax. A lower breathing reserve due to a high ventilatory demand and/or a low ventilatory capacity, which is more pronounced at a higher age, was associated with higher HRmax. Age explained the observed variance in HRmax by 72% and was improved to 83% when the variable “breathing reserve” was entered. DiscussionThe presented findings indicate an independent association between the breathing reserve at maximal exercise and maximal heart rate, i.e. a low individual breathing reserve is associated with a higher age-related HRmax. A deeper understanding of this association has to be investigated in a more physiological scenario.

High Mid-Flow to Vital Capacity Ratio and the Response to Exercise in Children With Congenital Heart Disease.

Pulmonary mechanics may play a role in exercise intolerance in patients with congenital heart disease (CHD). A reduced FVC volume could increase the ratio between mid-flow (FEF25-75%) and FVC, which is termed high dysanapsis. The relationship between high dysanapsis and the response to maximum-intensity exercise in children with CHD had not yet been studied. The aim of this work was to examine whether high dysanapsis is related to the cardiopulmonary response to maximum-intensity exercise in pediatric subjects with CHD. We retrospectively collected data from 42 children and adolescents with CHD who had either high dysanapsis (ratio >1.2; n = 21) or normal dysanapsis (control) (n = 21) as measured by spirometry. Data extracted from cardiopulmonary exercise test reports included peak values of heart rate, work load, V̇O2 , V̇CO2 , and ventilation parameters and submaximum values, including ventilatory threshold and ventilatory equivalents. There were no significant differences in demographic and clinical parameters between the groups. Participants with high dysanapsis differed from controls in lower median peak oxygen consumption (65.8% vs 83.0% of predicted, P = .02), peak oxygen pulse (78.6% vs 87.8% of predicted, P = .02), ventilatory threshold (73.8% vs 85.3% of predicted, P = .03), and maximum breathing frequency (106% vs 121% of predicted, P = .035). In the high dysanapsis group only, median peak ventilation and tidal volume were significantly lower than 80% of predicted values. In children and adolescents with corrected CHD, high dysanapsis was associated with a lower ventilatory capacity and reduced aerobic fitness, which may indicate respiratory muscle impairments.

Respiratory Impairment and Dyspnea and Their Associations with Physical Inactivity and Mobility in Sedentary Community‐Dwelling Older Persons

To evaluate the prevalence of respiratory impairment and dyspnea and their associations with objectively measured physical inactivity and performance-based mobility in sedentary older persons. Cross-sectional. Lifestyle Interventions and Independence for Elders Study. Community-dwelling older persons (n = 1,635, mean age 78.9) who reported being sedentary (<20 min/wk of regular physical activity and <125 min/wk of moderate physical activity in past month). Respiratory impairment was defined as low ventilatory capacity (forced expiratory volume in 1 second less than lower limit of normal (LLN)) and respiratory muscle weakness (maximal inspiratory pressure <LLN). Dyspnea was defined as moderate to severe ratings on the modified Borg index, immediately after a 400-m walk test (400-MWT). Physical inactivity was defined according to high sedentary time as the highest quartile of participants with accelerometry-measured activity of <100 counts/min. Performance-based mobility was evaluated using the Short Physical Performance Battery (≤ 7 defined as moderate to severe mobility impairment) and 400-MWT gait speed (<0.8 m/s defined as slow). Prevalence rates were 17.7% for low ventilatory capacity, 14.7% for respiratory muscle weakness, 31.6% for dyspnea, 44.7% for moderate to severe mobility impairment and 43.6% for slow gait speed. Significant associations were found between low ventilatory capacity and slow gait speed (adjusted odds ratio (aOR) = 1.41, 95% confidence interval (CI) = 1.03-1.92), between respiratory muscle weakness and moderate to severe mobility impairment (aOR = 1.42, 95% CI = 1.03-1.95), and between dyspnea and high sedentary time (aOR = 1.98, 95% CI = 1.28-3.06) and slow gait speed (aOR = 1.70, 95% CI = 1.22-2.38). Respiratory impairment and dyspnea are prevalent in sedentary older persons and are associated with objectively measured physical inactivity and poor performance-based mobility. Because they are modifiable, respiratory impairment and dyspnea should be considered in the evaluation of sedentary older persons.

Ventilation-limited exercise capacity in a 59-year-old athlete

Aerobic exercise performance may be limited by the respiratory system in fit elderly adults whose lungs undergo the normal ageing process or who develop lung diseases but can maintain high pulmonary blood flows and ventilatory requirements. Here we describe a 59-year-old athlete demonstrating high aerobic exercise performance limited by his relatively low ventilatory capacity. The male hobby cyclist (59 years, 176 cm, 83 kg), undergoing cardiopulmonary exercise testing, reported no complaints except a history of dyspnoea and exercise intolerance at high altitude (> 2000 m). Lung function testing indicated mild airway obstruction (FEVC: 4.22 l, FEV1: 2.91 l, FEV1/FEVC: 69%) which was not reversed post-bronchodilator. However, FEV1/FEVC was slightly above the 5th percentile and thus not confirming the diagnosis of COPD. The athlete completed 300 W (3.6 W/kg) and his maximal oxygen uptake was 45 ml/min/kg (156% predicted!). Above 250 W he was unable further increasing minute ventilation, and oxygen pulse and oxygen uptake even decreased. The related changes of the respiratory pattern (increase of breathing frequency, decreases of inspiratory capacity and tidal volume) indicated dynamic lung hyperinflation resulting in cardiac output constraint, arterial oxygen desaturation, severe dyspnoea and exercise limitation. This case report delineates the pathophysiological situation of ventilation-limited exercise capacity in a well-trained middle-aged subject. However, beneficial adaptations to regular exercise may have helped maintain high aerobic performance without any adverse symptoms during submaximal exercise.

Longitudinal study of respiratory findings in rubber workers.

A cross-sectional assessment of respiratory function and symptoms was performed in 1985 on 409 male rubber workers and 172 unexposed control workers. A follow-up study in 311 of the original rubber workers was performed 6 years later. Ventilatory capacity was measured by recording maximum expiratory flow-volume (MEFV) curves. At the time of the initial study, significantly higher prevalences of all chronic respiratory symptoms, except for asthma, were found among the rubber workers compared to controls. Smokers had a significantly higher prevalence of most of the chronic respiratory symptoms compared with nonsmokers. A high prevalence of acute symptoms during the workshift was recorded among the rubber workers at both surveys. Rubber workers demonstrated significantly lower ventilatory capacity measurements compared to predicted. Ventilatory capacity measurements diminished significantly across the workshift, particularly FEF50 and FEF25. Metaproterenol inhaled at the end of the workshift significantly improved lung function in a small group of sensitive rubber workers. Annual lung function loss among both smokers and nonsmokers was in excess of predicted. Our data suggest that exposure to noxious agents in the rubber industry are associated with the development of acute and chronic respiratory impairment.

ABC of Sports Medicine : PULMONARY LIMITATIONS TO PERFORMANCE IN SPORT

Assuming lung function to be normal, there is said to be no pulmonary limitation to aerobic performance. Justification for this statement rests with the fact that, while exercising at the maximum aerobic capacity (that is, when the rate of oxygen consumption cannot be further increased (VO2max)), it is possible to increase ventilation still more by voluntary effort. The main limiting factor is held to be a failure to match the rate at which muscle can consumes oxygen with the rate at which oxygenated blood can be delivered; in other words, the cardiac output. The lungs may be regarded as the carburetter of the engine, thus only when they are diseased—such as in chronic bronchitis or emphysema— does ventilatory capacity become reduced to the point where it limits exercise tolerance. Chronic bronchitis causes obstruction to air flow which, coupled with a reduction in vital capacity, results in a low ventilatory capacity or minute volume. Emphysema imposes an additional burden because not only is minute volume reduced but so also is oxygen transfer because of a loss of alveoli. High ventilatory capacity is essential for sports such as rowing, cycling, and middle and long distance running. When exercised to maximum most elite athletes in their mid-20s reach a respiratory rate of around 55 breaths a minute with a heart rate of close to 200, regardless of their size. In absolute terms the highest minute ventilation is usually achieved by the biggest athletes, as breath volume is directly related to size. Indeed the highest so …

Metabolic Acidosis during Exercise in Patients with Chronic Obstructive Pulmonary Disease: Use of the V-slope Method for Anaerobic Threshold Determination

Patients with chronic obstructive pulmonary disease (COPD) usually have limited exercise tolerance owing to low ventilatory capacity. Because metabolic acidosis induced by exercise increases ventilatory drive, decreasing the hydrogen ion stimulus may improve exercise capacity. However, in those with mechanical limitation to ventilation or chemoreceptor insensitivity, identifying metabolic acidosis may be difficult using gas exchange methods that depend on the ventilatory response to the acidosis. We compared a modification of a gas exchange method (V-slope) for determining the lactate (anaerobic) threshold (AT), which is independent of ventilatory response with a method using the change in blood standard bicarbonate (HCO3-) level in COPD and normal subjects during cycle incremental exercise. In 43 normal subjects, the VO2 at which metabolic acidosis was identified using the two method correlated (r = 0.75), although mean values differed. In 22 patients with moderately severe to severe COPD, eight who had a change in standard HCO3- less than 2.0 mEq/L between rest and 2 min of recovery from exercise (group 1) were contrasted with 14 whose blood standard HCO3- fell by greater than 2.5 mEq/L (group 2). Mean VC was higher and FEV1/VC was lower in group 2, but mean FEV1, maximal voluntary ventilation, and diffusing capacity for carbon monoxide were not different. The degree of obstruction did not correlate strongly with the degree of exercise metabolic acidosis. The AT determined by the V-slope method was compared with that from standard HCO3-; good correlation between these methods was found (r = 0.98), although mean values were different. The V-slope method predicted metabolic acidosis in 10/14 who had a fall in HCO3- more than 2.5 mEq/L. A significant proportion of patients with COPD seem to develop metabolic acidosis during exercise. The V-slope gas exchange method may be useful in selecting those patients with COPD who develop exercise metabolic acidosis and might therefore benefit from exercise training.

VENTILATORY CAPACITY ON EXPOSURE TO JUTE DUST AND THE RELEVANCE OF PRODUCTIVE COUGH AND SMOKING TO THE RESPONSE

The ventilatory capacity of 46 men exposed to jute dust in the manufacture of felt and wadding was estimated at the beginning and end of shifts on the first and last days of a working week. A smoking history was obtained from all subjects, and for those speaking English a more detailed questionnaire on respiratory symptoms was completed. Each man was also instructed to cough under observation, and a loose cough, as judged by ear or by production of a sputum specimen was recorded as productive. A significant mean decrease in forced expiratory volume at one second was observed in the series as a whole on the first day at work, but no significant change was found over the final day nor over the entire week. Closer analysis reveals that this decrease was largely confined to those with a productive cough on request, and to those who smoked, most of the former group being smokers. In these groups the decrease observed on the first day tended to persist throughout the week. Insofar as those who smoked, and particularly those who had a productive cough, tended to have a lower F.E.V._1·0, expressed either in absolute units or as a percentage of the forced vital capacity, the men with the greater initial impairment of ventilatory capacity showed the more significant decreases on exposure to dust. Evidence is produced to suggest that the sign of productive cough defines better than the history a group with a lower ventilatory capacity and a greater tendency to react to inhaled irritants.